[PATCH] powerpc/85xx: DTS - re-organize the SPI partitions property

[Hu Mingkai-B21284]

> -----Original Message-----
> From: Wood Scott-B07421
> Sent: Tuesday, September 24, 2013 7:03 AM
> To: Hu Mingkai-B21284
> Cc: Wood Scott-B07421; linuxppc-dev at ozlabs.org
> Subject: Re: [PATCH] powerpc/85xx: DTS - re-organize the SPI partitions
> property
> 
> On Tue, 2013-09-17 at 06:06 -0500, Hu Mingkai-B21284 wrote:
> > Scott,
> > Sorry for the delayed response.
> > Please fine my comments.
> > Thanks,
> > Mingkai
> >
> > > -----Original Message-----
> > > From: Wood Scott-B07421
> > > Sent: Thursday, September 12, 2013 9:16 AM
> > > To: Hu Mingkai-B21284
> > > Cc: Wood Scott-B07421; linuxppc-dev at ozlabs.org
> > > Subject: Re: [PATCH] powerpc/85xx: DTS - re-organize the SPI
> > > partitions property
> > >
> > > On Tue, 2013-09-10 at 21:07 -0500, Hu Mingkai-B21284 wrote:
> > > >
> > > > > -----Original Message-----
> > > > > From: Wood Scott-B07421
> > > > > Sent: Wednesday, September 11, 2013 7:33 AM
> > > > > To: Hu Mingkai-B21284
> > > > > Cc: linuxppc-dev at ozlabs.org
> > > > > Subject: Re: [PATCH] powerpc/85xx: DTS - re-organize the SPI
> > > > > partitions property
> > > > >
> > > > > What happens to exsting users whose flash is laid out the
> > > > > existing way, when they upgrade to these device trees?
> > > > >
> > > >
> > > > The SPI flash layout should be mapping the new device tree.
> > > >
> > > > If the existing device tree is used to deploy the SPI flash, the
> > > > following issues must be run into as the commit message described:
> > > >
> > > > 1. Kernel images would be overlapped with U-Boot image.
> > > > 2. Kernel images would be overlapped with FMAN ucode.
> > > > 3. Saving environment variables will crash the kernel image.
> > >
> > > Has the SPI U-Boot image always been larger than 512K for all these
> > > platforms?  Why, given that we're under 512K for other boot modes?
> > >
> >
> > For DPAA platform, the ld script used to link the u-boot image is
> > "./arch/powerpc/cpu/mpc85xx/u-boot.lds" which will generate the 512K
> > u-boot Image. This image will be split into 64bytes and appended PBL
> > command for Each 64bytes pieces, so the size of final image must be
> greater than 512K.
> 
> What is the entry point in SRAM when you load from PBL?  If it is (or can
> be made to be) the beginning of the image rather than the end, then turn
> off the resetvec and the fixed image size that results.
> 

1. Thus a special ld script need to be provided.
2. Now the spi image size is about 540KB, that's to say the PBL needs about ~30K
   for PBL commands. It's hard to save such a big space even we turn off the
   resetvec.

> > > > > We really should not be putting partition layout info in the
> > > > > device tree to begin with...
> > > > >
> > > > OK, I will remove the layout diagram in the commit message.
> > >
> > > That's not what I meant.  I meant that the dts should be describing
> > > hardware, and this is the sort of trouble we run into when we
> > > deviate from that.  A better way would be to use the mtdparts command
> line option.
> > > Even better would be some sort of on-flash partition table.
> > >
> >
> > You're right, but maybe some customer has already used the device tree
> partition table...
> 
> My main point was to encourage us to shift away from this rather than to
> rip it out right this instant.
> 

Yes, that's the correct way we should go.
Would you please pick up this patch first to resolve current issue we faced?
And we can consider to use the mtdparts or on-flash partition table for long term.

Thanks,
Mingkai